A biochemical approach to the evolution of procyanidins in grape seeds during the ripening of red grapes (Vitis viniferal. cv. Merlot Noir)

Abstract

Seed extracts of one clone of Merlot Noir were studied during maturation using low-pressure and high-performance liquid chromatography to observe changes in composition and to follow the evolution of the main procyanidins. These observations have prompted our laboratory to investigate the polymerisation of procyanidins associated with their extraction with an alcoholic solvent. We report the observed correlations for procyanidin dimers, which are relatively high between procyanidins B 2 /C 1 /A 2 themselves (linked by C 4 -C 8 bond), but which are non-existent between procyanidins linked by C 4 -C 8 and by C 4 -C 6 bonds. These observations have enabled us to propose a hypothesis regarding procyanidin oligomer biosynthesis.

Changes of Flavan-3-ols with Different Degrees of Polymerization in Seeds of ‘Shiraz’, ‘Cabernet Sauvignon’ and ‘Marselan’ Grapes after Veraison

“…For each grape cultivar, three monomers all showed a fluctuating decline in their contents from grape veraison to commercial harvest, and a rapid decrease in total content occurred from the onset of veraison to four weeks after veraison ( Figure 3 ). It has been suggested that the decrease of flavan-3-ol content in grape seeds is probably due to flavan-3-ol polymerization and oxidation [ 30 , 31 ] or flavan-3-ols binding with other components, such as proteins and polysaccharides [ 22 , 23 , 26 , 31 , 32 ]. As a result of this, extractable flavan-3-ols decrease.…”

“…It is thus suggested that the decrease in the relative proportion of monomers or even oligomers may contribute to the increase in that of polymers. Gaulejac et al [ 30 ] have also pointed out that the increase of the proportion of polymers should be attributed to the polymerization of flavan-3-ols with lower DP.…”

Seed Maturation Dynamics in Cabernet Sauvignon and Pinot Noir Grapes During Berry Ripening in Cool Climate Zones

“…At veraison, the berries reach a pivotal point where tannins and flavan-3-ol monomers reach their maximum concentration, which subsequently decrease by up to 60 and 90%, respectively. ,, This decline is likely connected to a reduced expression of genes responsible for proanthocyanidin synthesis after veraison . Additionally, enzymatic oxidation and a reduced permeability of the integument further reduce the concentration. , Conversely, some studies have reported opposite developments during ripening, with no significant changes or even an increase in tannin concentration. − Furthermore, the association of proanthocyanidins with cell wall polysaccharides ,, or proteins leads to reduced extractability. Anthocyanins affect these interactions between tannins and cell wall polysaccharides, which has the potential to conversely increase the extraction of tannins again .…”

Comparison of Proanthocyanidins with Different Polymerisation Degrees among Berry Skins of ‘Shiraz’, ‘Cabernet Sauvignon’, and ‘Marselan’

“…The biosynthesis of PAs occurs mainly in the early stages of berry development and ends around véraison. The content of PAs decreases from véraison to ripening, possibly because they bind to proteins on the internal surface of the tonoplast and to polysaccharides on the cell wall (De Gaulejac et al, 1997). Cell wall extension during berry ripening increases the PA-binding capacity on cell walls, and the structure and degree of polymerisation of PAs also influence their affinity for binding materials (Hanlin et al, 2010;Bindon & Kennedy, 2011).…”